Year 9 Interactive Maths - Second Edition

Problem Solving Unit

Problem 7.1  How Far?

How far will a train travelling at 72 km/h go in 1 second?

Problem 7.2  A Car

A car travelling at a speed of 36 km/h covers a distance of 1000 cm in 1 second.  How many centimetres per second is covered by a car travelling at a speed of 54 km/h?

Problem 7.3  A Long Chain

It costs $2 to open a link and $3 to weld it closed.  A lady wants to join the six pieces shown above into one long chain.  What is the maximum cost?

Problem 7.4  Brine Solution

We have 1000 mL of a 20% solution of a brine.  How much water should be added to make it a 10% solution?

Problem 7.5  A Record

A table tennis team has won 5 of its 7 games.  How many of the 8 remaining games will the team need to win to have a season record of winning 80% of its games?

Problem 7.6  A Car Tyre

A car tyre has two punctures.  By itself, the first puncture would make the tyre flat in 15 minutes.  By itself, the second puncture would make the tyre flat in 12 minutes.  How long will it take for both punctures together to make the tyre flat (assuming that the air leaks out at a constant rate)?